The present invention relates to methods of increasing miscibility between natural oil polyols (NOP) and petroleum-derived polyols (e.g., petroleum-based or pretro polyol) such as aromatic and aliphatic polyester polyol and polyether polyol.
The preparation of polymers from renewable resources is of significant economic and scientific importance. Natural oil polyols, also known as NOPs or biopolyols, are polyols derived from vegetable oils by several different techniques. Vegetable oils have a number of excellent properties that can be utilized in producing valuable polymeric materials, such as but not limited to polyurethanes. Vegetable oils are characterized by their hydroxyl values and fatty acid compositions. NOPs are generally hydrophobic, due to their branching, triglyceride-based structures. Modified soy-based vegetable oil polyols can be used as a replacement for conventional polyols, reacting with isocyanates to produce flexible feedstock polyurethane (PU) foams, elastomers, and coatings. Soybean oil (SBO) is highly hydrophobic, thus excellent weather stability of the soy-based PUs can be expected.
Unfortunately, NOPs also exhibit immiscibility with petroleum-based polyols. While not wishing to be bound by theory, it is believed that this limited miscibility is primarily due to structural differences between NPOs and petroleum-based polyols. FIG. 1 illustrates the chemical structure of two exemplary polyester petroleum-based polyols. FIG. 2 illustrates the chemical structure of four exemplary polyether petroleum-based polyols. These compounds are relatively hydrophilic due to the high number of ester and ether groups available to interact with water molecules due to van der Waals forces. FIG. 3 illustrates the chemical structure of two exemplary NOPs. As with most triglycerides, soy polyols have aliphatic tails joined with a hydrophilic head group.
U.S. patent application Ser. No. 11/524,603, filed Sep. 21, 2006, published as U.S. Publication No. 2008/0076901, now U.S. Pat. No. 7,674,925, which is incorporated herein by reference, describes a method of synthesizing soy-based polyols in one step. FIG. 4 illustrates this method. Namely, the unsaturated sites in soy oil are directly functionalized, without epoxidation, to yield soy polyols in a one-step process. For example, hydrogen groups, such as hydroxyls are efficiently and directly added to the olefin groups of plant oils. Suitable nucleophilic functional groups for synthesis of soy-polyols via this synthetic pathway include, but are not limited to amines, thiols and phosphines. Suitable active hydrogen functional groups include but are not limited to amines, thiols and carboxylic acids. A preferred designed reactant is a polyhydroxylalkyl amine. The reaction is catalyzed by molecules, which upon addition to the plant oil double bonds, yield good leaving groups. Examples of suitable addition catalysts include, but are not limited to: halogens of the structure X2 wherein X2 includes I2, Br2 and Cl2, and hydrohalogens of the structure HX wherein HX includes HI, HBr and HCl. Suitable reaction temperatures for synthesis of soy-polyols via this synthetic pathway are generally between about 120° F. (48° C.) and about 270° F. (132° C.)
According to a method of the invention described in U.S. patent application Ser. No. 11/524,603, natural oil polyols are produced by addition of a designed reactant, N-AH, to olefin groups of a plant oil wherein N includes at least one nucleophilic functional group and AH is a functional group having at least one active hydrogen or masked active hydrogen. The reaction is catalyzed by an addition reaction in which at least one of the functional groups added in the transition state by the catalyst is a good leaving group. A synthetic pathway according to the invention is as follows:

It is believed that the prevalence of the commercial use of the epoxide synthetic pathway to produce plant polyols is due to a general belief in the art, based upon the findings of numerous authors, that the unsaturated sites in plant polyols cannot be directly, efficiently functionalized to yield polyols. However, as shown above and described herein, a more desirable direct method is possible according to the present invention.
Suitable plant oils for use according to the invention are any plant oil or oil blends containing sites of unsaturation. Such suitable plant oils include, but are not limited to: corn oil, soybean oil, rapeseed oil, sunflower oil, sesame seed oil, peanut oil, safflower oil, olive oil, cotton seed oil, linseed oil, walnut oil and tung oil and mixtures thereof. It is also foreseen that other oils or blends of oils containing sites of unsaturation may be processed according to the invention, including but not limited to natural, genetic, biotic and blends thereof.
Suitable nucleophilic functional groups according to the invention include, but are not limited to amines, thiols and phosphines. Suitable active hydrogen functional groups according to the invention include but are not limited to amines, thiols and carboxylic acids.
A preferred designed reactant according to the invention is a polyhydroxylalkyl amine. For example, according to the invention, the hydroxyl groups of dihydroxyalkylamines that were used to make plant polyols of the invention include primary hydroxyl groups such as diethanolamine, and secondary hydroxyl groups such as bis(2-hydroxypropyl)amine. Preferred alkyl groups of dihydroxyalkylamines used according to the invention are those containing 2 to 12 carbon atoms such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups. Suitable amines of dihydroxyalkylamines of the invention are secondary amines, primary amines, and diamines such as N,N-bis(2-hydroxyethyl)ethylene diamine and N,N′-bis(2-hydroxyethyl)ethylene diamine.
Processes according to the invention are catalyzed by molecules, which upon addition to the plant oil double bonds, yield good leaving groups. Examples of suitable addition catalysts according to the invention include, but are not limited to: halogens of the structure X2 wherein X2 includes I2, Br2 and Cl2, and hydrohalogens of the structure HX wherein HX includes HI, Hbr and HCl. The halogen X2 functions as a starting catalyst and HX as a finishing catalyst. It is believed that the catalysis proceeds in a manner well known to addition chemistry to form an intermediate. The halogen X2 is added onto the carbon-carbon double bond of plant oil molecules. It is believed that the next step proceeds in a manner well known in SN2 chemistry, replacing the leaving group to form a novel plant polyol. Hydro-halogen HX undergoes addition reaction with a next plant oil molecule or next fatty acid branch of plant oil molecule to give a halogenation product, then the halogenated product undergoes replacement reaction with dihydroxylalkylamine to form the plant polyol and HX. The addition reaction and replacement reaction repeats until the designed reactant, e.g. dihydroxylalkylamine, completely disappears.
It is foreseen that other catalysts may be utilized according to the invention as long as such catalysts perform addition reactions to double bonds and in so doing add a good leaving group. Furthermore, according to the invention, halogen catalysts and hydro-halogen catalysts can be added to cold or hot plant oils. Halogen catalysts may be added to a plant oil in a first step, and once the halogen disappears, a designed reactant, such as a polyhydroxylalkyl amine may be added. Co-addition of the catalyst and the designed reactant is also possible. In a preferred process according to the invention, a hydro-halogen catalyst is added to a plant oil in a first step, followed by the addition of a dihydroxyalkylamine.
Suitable reaction temperatures of processes according to the invention are generally between about 120° F. (48° C.) and about 270° F. (132° C.). Reaction times typically depend on the identity of the catalyst and the reaction temperature. If the reaction is catalyzed by iodine or hydrogen iodide, the reaction is typically faster than reactions catalyzed by other halogen catalysts. The use of greater amounts of a catalyst typically shortens reaction time.
A preferred process according to the invention is the addition of a polyhydroxylalkyl amine molecule onto the olefin groups of a plant oil such as soybean oil. In particular, the designed reactant, a dihydroxlalklamine, contains a primary amine as the nucleophile and two hydroxyl groups as the active hydrogen groups. The reactant adds directly onto the molecule of plant oil in one step, giving a new plant polyol. The following is believed to be a possible mechanism for such a process:

A preferred process according to the invention is catalyzed by iodine. It is believed that an addition reaction occurs, with an iodine atom acting as a leaving group for the incoming nucleophile. It appears that the hydroxyl number of the plant polyol depends on the amount of dihydroxyalkylamine used in the addition reaction. Viscosity of inventive plant polyols of this application typically range between about 250 cps and about 450 cps at room temperature (about 77° F. (25° C.)), which is considered in the art as quite low for a soy polyol. In contrast, commercially known plant polyols typically have a high viscosity, ranging between about 1,200 cps and about 20,000 cps, depending on the hydroxyl number. The high viscosity of known plant polyols can cause mixing difficulties during the formulation of polyurethane.
Furthermore, known plant polyols often have low reactivity due to steric hindrance caused by the presence of secondary alcohols. Such low reactivity yields polyurethanes with poor physical properties. In contrast, plant polyols of the present invention may be designed to contain only primary hydroxyl groups that are known to be quite reactive. Also, in contrast to current epoxide synthetic pathway technology, processes according to the invention result in fewer by-products, as evidenced by the comparatively lower viscosity and lighter color of plant polyols produced according to the invention. In light of these superior properties, good polyurethane foams and elastomers can be made directly from polyols made according to the invention, without using other polyols. Thus, polyols derived from fossil fuels may be completely replaced by plant polyols in the production of polyurethanes, in a cost effective manner, by using the methods and plant polyols according to the invention.
Polyurethanes may be produced by reacting the plant polyols of the invention with a variety of isocyanates, including but not limited to aromatic isocyanates, aliphatic isocyanates, and isocyanate terminated pre-polymers. The physical properties of polyurethane made from the inventive plant polyols depend on the polyols, the formulation and the isocyanate used. Preferred isocyanates include diphenylmethane diisocyanate (MDI) and polymeric diphenylmethane diisocyanate. Other suitable isocyanates include toluene diisocyanate (TDI), methylenebis(cyclohexyl) isocyanate (H12MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and adducts and pre-polymers of such isocyanates.
It is well known that hydrophobic liquids do not mix well with hydrophilic liquids. However, if the miscibility between NOPs and petroleum-based polyols can be improved, NOPs can serve as renewable resources as feedstocks for chemical processes that will reduce the environmental footprint by reducing the demand on non-renewable fossil fuels currently used in the chemical industry and reduce the overall production of carbon dioxide, the most notable greenhouse gas.